Antiozonants and antiozonant compositions for elastomers



E. E. STAHLY Nov. 17, 1964 ANTIOZONANTS AND ANTIOZONANT COMPOSITIONS ORELASTOMERS Filed Aug. 28, 1956 4 Sheets-Sheet l INVENTOR.

ELDON E. STAHLY E. E. STAHLY Nov. 17, 1964 ANTIOZONANTS .AND ANTIOZONANTCOMPOSITIONS 0R ELASTOMERS Filed Aug. 28, 1956 4 Sheets--SheelI 2INVENTOR.

ELDON E. STAHLY Nov. 17, 1964 E.. E. s'rAHLY ANTIOZONANTS ANDANTIOZONANT COMPOSITIONS OR ELASTOMERS Filed Aug. 2.8, 1956 4Sheets-Sheet 5 XVM BNlddVtlVcl SilVd E. E. STAHLY Nov. 17, 1964ANTIOZONANTS AND ANTIOZONANT COMPOSITIONS OR ELASTOMERS Filed Aug. 28,1956 4 Sheets-Sheet 4 JNVEN TOR.

ELDON E. STAHLY United States Patent O 3,157,615 ANTIGZQNANTS ANDANTGZNANT CGP/EPO- STNS FR ELASTQh/ERS Eldon E. Stahiy, Birmingham,Mich., assigner, by direct and mesne assignments, of three-fourths toQiiver i Burke, 5r., Grosse Pointe, Mich., and one-fourth to EastmanKodak Company, Rochester, NX., a corporation of New Jersey Filed Aug.28, 1956, Ser. No. 696,767 5 Claims. (Cl. 269-453) The inventiondisclosed herein relates to antiozonants for high polymers per sesubject to ozone attack, especially vulcanizable elastomers includingthe natural rubbers, synthetic elastomers such as polybutadiene, GR-Stype synthetic rubbers, other diene vinyl copolymers such asacrylonitrile-butadiene elastomers, etc., and in addition thenon-vulcanizable elastomers, plastomers and resins, particularly thosewhich have residual unsaturation, and aims generally to improve thesame.

The present invention includes the class of substitutedparaphenylenediamine antiozonants for elastomeric material set forth inTable A, synergistic antiozonant combinations thereof with either wax orantioxidant materials or with both, the incorporation of saidantiozonants and synergistic combinations in elastomers, the improvedproducts resulting therefrom, and the new chemical compounds hereindisclosed.

The antiozonants of this invention also exhibit synergism with certainheavy metal soaps, a fact discovered jointly by applicant and R. G.Spain, and certain of the new antiozonants of the present invention havebeen disclosed in copending joint U.S. application, Ser, No. 523,711,filed July 22, 1955, for showing the synergism of that joint invention.However, such new antiozonants and combinations thereof with elastomers,per se, and in synergism with wax and/ or antioxidant are not claimed insuch joint application, since these matters are the sole invention ofpresent applicant and claimed herein.

Similarly certain of the cyanohydrocarbon derivatives found by thepresent inventor to be effective antiozonants are, as chemical compoundsdisclosed and claimed in the U.S. application of applicants co-worker,Rene G. .lennen, Ser. No. 556,423, now Patent No. 3,038,868, filedDecember 30, 195:5, who iirst p-repmed them as part of a group ofcyanoalkylamines for other uses, many of which per se are notantiozonants. Accordingly it is the discovery of the antiozonantcharacteristics of a particular class of such cyanohydrocarbonderivatives, some 0f which were chemical compounds available from Dr.Jennen, and not the available chemicals per se, that is claimed hereinas the invention of the present applicant in connection with that partof the invention herein set forth in Table A, and the new chemicalcompounds herein disclosed, and set forth in Table B, exclude allcornpouncls available from Dr. Jennen as weil as from other sources.

While only the particular classes of the cyanoalkylamines set forth inTable A have been found to be effective antiozonants, per se, thecyanoalkylamines as a class do exhibit rubber antioxidantcharacteristics, and have been found by the present applicant to beeffective synergists when combined with antiozonants of the presentinvention, and hence are referred to hereinafter as antioxidantsemployable for forming synergistic combinations of the presentinvention.

Patented Nov. 17, 1964 ice Similarly, certain of the di-sec-aminesthat'are parent compounds for derivatives of the present invention setforth in Table A, are per se effective antiozonants, and are claimed assuch in copending applications by the present inventor in the case ofthe N-cyclohydrocarbon Nalky1 substituted phenylenediamine antiozonants,and in said joint U.S. application S.N. 523,711 in the case of thel\l-aryl-Ncycloalkyl substituted phenylenediamine antiozonants.

PROLOGUE AND OBJECTS It is well known that many compounds possess theproperty of preserving rubber, when incorporated therein, against thesupercial hardening and crazing resulting from attack by oxygen, lightand heat. Such compounds are termed antioxidants However, as pointed outin said copending joint application, the previously known antioxidantshave not been effective to guard against the distinctly diierent effectsof ozone on such materials, of which the generation of deep penetratingcracks is characteristic.

It has long been recognized that a solution of the problem of ozoneattack on both natural and synthetic rubber goods is greatly needed andthat reduction or freeing of such goods from ozone attack is of highimportance to both civilian and military consumers. Indeed, as early as1944 the ASTM prescribed a testing procedure for measuring ozone attackin connection with essentially static goods, such as refrigeratorgaskets, windshield mountings and the like.

It has more recently been recognized that when dynamically flexed rubbergoods, such as tires, are made in the usual way with or withoutantioxidants, such articles are subject to deterioration by ozoneattack, whether in continuous or intermittent use or storage.

As above noted, attack by ozone on statically or dynamically employedrubber goods becomes apparent by the development of penetrating crackswhich progressively become deeper with time of exposure to theatmosphere, which practically always contains ozone in trace amounts.Such cracks in tires often become suciently deep to cause failure.Indeed, in the case of new tires stored for substantial periods, suchcracks may cause failure Within a relatively short time after the tiresare put into use. This result of ozone attack is thus quite distinctfrom the development of fine surface cracks, i.e., checking and crazing,attributed to oxidative deterioration.

Ozone attack is extremely bad in areas indigent to cities such as LosAngeles, California, where smog conditions are associated with highozone concentration, c g., from 10 parts to 60 parts per hundredmillion. In Los Angeles and similar high-ozone areas so-called ozonecracks may develop in rubber articles such as tires, in less than amonth of storage time. 'In areas such as Detroit, Michigan, the Vnormalozone concentration in the air is less than 5 parts per hundred million,and ozonev cracks may not develop for several months.

In any event ozone-cracking is recognized as one of the heretoforeimportant unsolved problems in storage and use of both civilian andmilitary articles containing natural or synthetic rubber components, andthe inventions in said copending applications, and herein 'aim t0provideV solutions for that problem, especially with respect toelastomers employed in dynamic usage;

For many years the rubber industry has employed chemicalsV such asSantoex AW (theV trade name for6ethoxy-2,2,4trimethyl1,2-dihydroquinoline) in rubber articles toprotect the same against oxidation on aging. From a survey of chemicalsused to protect the products of representative manufacturers of rubbergoods, it apelastomer stocks'. Certainrcompounds including benzidine Kadditives caused overfcuriug, thus rendering them unsuitpears thatSantoex AW had beenV Widely accepted and able for use in GR-S stocks formanufacture of tires and used as one of the best materials available forthat purmany other articles of commerce.

pose. Accordingly, to demonstrate the ozone resistance n Thus, principalobjects of the present inventionare the aiorded by new antiozonants, aGR-S compound, con-Y Vprovisions Voi (l) new antiozonants or chemicalcom-V taining S'antoflex AW, was compared with GR-S containpounds forincorporation into elastomer and plastomer ing other antioxidantmaterials to demonstrate which of l() compositions which alone willeectively protect same such materials seemed the most resistant to ozoneattack against ozone cracking, especially after heataging, (2) aftersubjecting to heat aging conditions, and since theSynergistic'cornbinations of said new ,antiozonantsf withY Santoex AWseemed to be the best of the materials known antioxidants for rubberand/ or waxes which willL so compared, though itself aording no adequateproteceQCVY Protect he Same against OZODSCaCkIl-SPC- Y tion 0felastgmers lagainst 020116 attack, it was usgd a3 n, Clllly fll aging Olheal aging, WlhQll dletllOUSlyalastandard for comparison to evaluate theimproved resistfn" h Physical lOl'Ol'eeS 0f the Pfoecfed materials, anceto such attacks imparted by new and vsynergistic (3) new methods ofprotecting elastomers and'plastomersV antiozonant compositions (seeTable I of copending joint from ozone attack characterized by the use ofsuch ne application,v Ser. No. 523,711, led July Z2, 1955). In 2Qmaterials, and (4) elastomer and plastomer Varticlesninspite of theaccepted usage of Santoilex AW in the including such chemicalsandgrendered ozone resistant dustry it will Vbe noted from the tableshereinafter, in thereby. Other objects and advantages of the inventionwhich this material Vis used as control, Ythat relatively will be madeapparent kfrom ythe following more detaile little protection ofelastomers against ozone cracking is description and examples oi' itsapplication. o j afforded by Santoflex AW as compared to the anti- 5 Theinvention resides in the new antiozonants and cornozonants of thepresent invention, particularly afterV the pounds herein disclosed, thesynergistic combinations samples had been heat-aged, thus simulating theconditions thereof with antioxidants and/ or waxes, the methods ofaccompanying subjection of the elastomers to dynamic Y applying said newantiozonants and synergistic combinausage, n tions, and the improvedproducts containing the same.

Adesirable propertyV in case of antiozonants, as in the This inventionthus comprises, inter alia, (l) the new case of any other additives torubber, is inertness with reand useful antiozonants for rubber Yfallinginto the gen- Vspect to the curing ingredients ofthe elastomer compound.eral class and categories Yset forth in Table A, which are Thevulcanized compounds after exposure to Aheat-aging subject to therestrictions and limitations therein set forth, (.24 hours at 100 C. istaken as an exacting standard and (2) those of said new antiozonantsthat are, new andr herein) shouldl still show from about 275% to 375% orpreviously unknown chemical compounds, per se, and greater elongation tobe suitable for tire stocks. Original hence patentable as such, thatfall into the general classV and heat-aged stress-strain properties weretherefore both Y and categories set forth inTable B, and which aresubjectV obtained Vto demonstrate that normal vulcanizations are to therestrictions and limitations therein set forth, as willV obtainable withthe antiozonants incorporated in the elasbe apparent from the followingdetailed description and tomer compounds. For the sake of brevity, thetensile examples, which are to be taken as illustrative and notproperties have been omitted frornthe table wherein the restrictive ofthe invention, the scope of which is more samples showed the VphysicalYproperties required of the Y v particularly pointed out in theA appendedclaims.

Table A CATEGORIES OF ANTIOZONANTS ACCORDING TO THE PRESENT INVENTIO YFORMULA R--NA-.Vl`tN.`B--RIv N, HAVING THE GENERAL Limitationtotalcarbons R Y Either of A and B (selected from) R' `(selected from) TheSecond of A and B R in R +hydro- (selected from) carbon sub stltutentsR,A,B,andR" t Y l. Non-Polar: Unsubstituted or l. Non-Polar:V

I (a) hydrogen alkyl substi- =alkyl (Cz-C4) p (b) alkyl (C1-C4)V tutedp-phenyl- 2. Polar: Y pn-alkyl 2. Polar: ene and p- Y (a) Halogenoid andOrgano` =secalkyl 15-32 Y v (a) -Halogenold and Qrganodiphenylenehalogenoid substituents, II Y halogeuold substituents, c radicals. eg.:e.g..: Y Y (1) nitrosof -alkyl (1) mtroso- (2) cyano(C1-C1n) hydro--aryl or cycloalkyl 11i-31'V (2) cyano (C1-Cio) hydrocarbon, includingaand (unsubstltuted carbon, including aand -cycloalkyl, and -cycloorhydrocmbon )5P-cycloalkyl; and -cycloallrenyl substituents, per sesubstituted), alkenyl substituents, per se and substituted with alkyl,HI and substituted with mlryL, cycloalkyl, and ary cycloalkyl, andarylradicals. -cycloalkyl g radicals. K Y V(3) Polycyauoalkyl poly-V-cycloallryl 16-31 (unsubstl- (3) P olycyauoalkyl polyamines, eg.,cyanohydro- (unsubstltuted v tuted or n amines, e.g., .cyanohydrocarbonsubstituted poly or hydrocarbon hydrocarbon carbon substituted poly(alkyleneaminV-alkyl substituted). substituted) (a1kyleneamlno)alkylsubstitutnents.

substituents. (b) AcyKOa-Cio) -scoallryl y -ssc-alkyl l2f-32 Cyclcallryl-aryl 17-31 Table B CATEGORIES or NEW AND USEFUL COMPOUNDS ACCORDING ToTHE PRESENT INVNTIO'N, HAVING 'PHE GENERAL FORMULA R-NARNBR"Limitationtotal carbons R Either of A and B R Second of A and B R" inR+hydro carbon substituents R, A, B, and R" I Same as in Table A. Sameas in Table Same as in Table A except that A. when polar group 2(a) (2)is -prl-alkyl employed, other of A and B sec-alkyl -32 must be otherthan 1(a) and 11a 2am).

-alkyl cycloalkyl (un- 13-31 substituted or hydrocarbon substituted) IIbpr1-alkyl aryl (unsubsti- 13-31 tuted or hydrocarbon substituted).

III

-cycloalkyl cycloalkyl (un- 16-31 (unsubstituted) substituted orhydrocarbon substituted) -sec-alkyl -sec-alkyl 12-32 cycloalkyl aryl17-31 As is evident from Tables A and B, the materials contained hereinare all derivatives of monoand di-arylene diamines, which in all casesare N,Ndihydrocarbon radical substituted. The substituents A and B,Where other than hydrogen, may be introduced into the parentN,Ndisubstituted amines by reacting the latter with appropriate reagentsas hereinafter described, or in other Ways.

For simplicity of production it is preferred that each amino group ofthe parent compound be secondary and that the substituents of thesubstituted p-phenylenediamine antiozonant be hydrocarbon groups,preferably identical, although certain advantages are found for the useas parent materials of substituted p-phenylenediamines wherein one or"the amino groups is substituted with an alkyl radical and the otheramino group is substituted with a cyclic hydrocarbon substituent.Derivatives found in which A and/ or B are other than hydrogen havedeiirute advantages over the parent compound. For example, advantages inScorch time and/or aging characteristics of the elastomer compounds inwhich the said antiozonant is incorporated, or in other characteristics.

Also, While for greater antiozonant activity, it is preferred that R' bean unsubstituted or hydrocarbon substited phenylene radical, Within thebroader aspects of the invention (see Tables A and B), diphenyleneradicals selected from the group consisting of biphenylene,methylene-diphenylene, and iminodiphenylene, unsubstituted andhydrocarbon substituted, may be employed as R. The NJW-substituted,p-diamino-diphenylenes have been shown in the above identified jointapplication to have antiozonant activity, and the present invention hasshown that the derivatives of these materials corresponding to those ofTable A are similarly improved by the designated substituents at A andB.

In addition to the new compositions of matter of Table B I havediscovered a new class of useful compounds which are represented byRNAR-N=R" wherein R is a hydrocarbon radical including acyclic andcyclic hydrocarbon radicals, R is a monoor diphenylene radical ashereinbefore defined, A is any of the substituents listed for either Aor B of Table A, and R" is a hydrocarbon radical joined to the nitrogenby a double bond.

The appropriate incorporation of the new antiozonants gives virtualimmunity against much higher than ordinary atmospheric concentrations ofozone to elastomer compositions even when the same have been subjectedto radical heat-aging, thus showing that these antiozonants are capableof protecting the products for long periods of time under conditions ofdynamic usage as Well as in static usages.

In the accompanying drawings pertaining to representative categories ofthe invention:

FGURES l and 4 are illustrative charts drawn to simple coordinates.

FIGURES 2 and 3 are illustrative charts drawn to semi-logarithmiccoordinates.

PREPARATION OF ANTIOZONANTS The parent symmetrical compounds of thisinvention may be prepared in a simple manner by aminative reductions ofketones with p-phenylenediamines and hydrogen. For example, one moleNI'lZ-CSH--NHZ plus 2 moles diisobutyl ketone plus hydrogen with ahydrogenating catalyst, such as copper chromite or Raney nickel, underthe influence of heat and pressure, produce N,N-disecondary-nonylderivatives of the diamines, namely,sec-nonyl-NH-CeH-NH-sec-nonyl. The above reaction can be run with onemole of a rst alkyl ketone per mole of p-phenylenediamine so that therst product contains sec-alkyl-NH-CsHg-NHZ, and this product can befurther treated with a second alkyl ketone to effect substitution in thesecond amino group, or it can be used itself as a parentmono-substituted amine for preparation of A and/ or B substitutedderivatives as described in the second paragraph following.

An advantageous method for preparation of N,N'di substitutedp-phenylenediamine wherein the substituents are not identical depends onreaction of p-nitroaniline and a ketone. The resultant p-nitro Schiffbase is hydrogenated in the presence ofa copper chromite, for example,to produce the coresponding thisdiamino product is then reacted with asecond ketone i in the presence of hydrogen and a catalyst to makeR-NHC6H4NHR.

When N.- phenyl-Nsec-alliyl-p-phenylenediamine or YN-cyclohexyl-N-sec-alkyl-p-phenylenediamine isy desired,

aniline or cyclohexylamine, respectivel may be reactedV withp-chloronitrobenzene to form p-nitrodiphenylamine orp-nitrophenylcyclohexylamine, respectively; which may then be reactedwith a ketone under Vhydrogenating l conditions to produce theunsymmetrical' antiozonants. When A and/ or B are other than hydrogenthe substituent groups such as methyl, nitroso, acyl, cyanoethyl andtetra(cyanoethyl)-diethylenetriaminoethyl are introducedl intoV theparent N,Ndisubstituted p-phenylenediamine.

Thus Vthe above described -morio-V and disubstituted amines are readilyreacted'by. heating in appropriate solvents i with (l)l methyl sulfate,(2) nitrous acid, (3) fattyracids,

polyalrlfrylenepolyamineV is illustrated by the reaction of N,N'di-Z-octyl-p-phenylenediamine with penta(cyano ethyrl)diethylenetriamineof Dr. lennens said copending U.S. application, S.N. 556,423.

must be used-in larger amounts when used as the sole j tion' comprisethose falling in categories I, II, III, lV and V set forth in Table A,above.

Specific ranges of these categories of materials (Table A) areantiozonants when used alone in amounts ofVDisubstitnted-p-phenyleiiediamine Penta(cyanoethyl)idiethylenetriamineabout 2 parts or more per 100 parts of the high polymers toV beyVprotected and are claimed as such herein. The amounts employed for themono-nitroso and mono-acyl derivatives of the p-phenylenediamines shouldbe increased to some extent (Examples A-2, -3 and"-4) because of theincrease in molecular weight of the diamine Vresultant from conversionto said derivatives. The last statement does not Vapply to the otherderivatives of this invention (e.g., Examples D-2, .3, B41, 2, C-9-l0).

Part Il of this invention discloses synergistic combinations of theantiozonants of Part I hereof with antioxidants and/or waxes.

The antioxidants that show this synergistic elect with the abovementioned antiozonants are members of' the Metal oxide y eg., Sn O HON.-i-

While this reaction mechanism has not been conclusively demonstrated,the reaction product of one mole of a Y poly('cyanoalkyl)- polyalkylenepolyamine. with one mole of disubstituted phenylenediamine in theYpresence'of'a trace of metal oxide is found reproducible and unique andpossessive of antiozonant properties (Examples B-l andE-2). Y. Y

Where only one of A or B is to be so substituted one mole of substituteddiamine is reacted with one mole of reactanty (l), (2), (3), (4), or(5). When both A and Y B are to be substituted one mole of thedisubstituted diamine is Vreacted with two moles'of (l), (2), (3), (4)

y or (5) respectively or a combination of any two thereof.

For example, appropriate solvents for electing these 4reactions are:water and dioxane'for methyl sulfate; Water for nitrous acid; andbenzene, if desired, for lactonitrile;

l no solvent being necessary for the'fatty acids and their derivatives;or for the polycyanoalkylpolyamines. 'Ifhere are other Vpracticalmethods of preparation, and the de scribed methods are mentionedasillustrativeonly.

GENERAL DESCRIPTION Y n The research'has shown that the newV compoundsare Valuable antiozonants forv plastomers and resins as well as fornatural andfsynthetic rubbers and are particularly useful antiozonantsfor-tires andlike'natural and syn'- thetic products subjectV toozonefatta'ck at high operating temperatures, 'such as thoseVtemperatures attained by heavyY duty truck tires, which Atemperaturesmay rise as .high as 300 F. in use. Antiozonants are herein dened Yfasadditive Vagents which protect the polymeric material, eg., naturalVand synthetic rubbers, against deteriorationV due to ozone attack.While serving as yantiozonants, the new compounds; also serve asantioxidants, ie., the new of tensile properties caused by'reaction ofvulcanized i rubberrwith oxygen." fHoweveiy'the Vnew) antiozonantsfollowing classes: amines and diamines; phenolics; Yhy- Y amounts thanabove stated, and even in amounts less thanr 2 .parts/100 parts of thehigh polymer to be protected, in combination with suitable proportionsof known rubber antioxidants and/ or certain thioamideantioxidants and/or waxes.

VFurther this invention includes thek incorporationp'of the newantiozonants of-Parts I and II ofrthis invention into `high polymericmaterials and into latices thereof, and

Y the ozone resistant productstherefrom, Y

' products ofY this invention protect against` deteriorationv It hasbeenrdisclosed in the aforesaid' copending joint US. application thatwhen NJW-,hydrocarbon substituentsV on the otherwise unsubstitutedp-phenylenediamineY con-'g tain less thanl 12 or more than 25 carbonatoms the vir-` ytual immunization against ozone is not obtained. Y VIt,is the applicants hypothesis that migrationV of theanti-` ozonant isnecessary to prevent ozone crack initiationV at the air-rubberVinterface, and that the ability of the` anti-Y ozonant'to migrategiscurtailed when the numberof carbon atoms constitutingthe'N,N'-substituentsis inexcess ofY about 25, and further that Vwhenthe number of carbonY atomsin such substituentsis too small theadditives mig; rate tothe surfaceY of the rubber compound and are4 losti by volatilization fromV heating or simple aging, and thuscannotVprotect 'therpr'oduct {Thus Yfor effective antiozoneiv activitycompatibility, migratability,v and volatilityrof the diamineantiozonantof this inventionarje important inter-.7, dependent characteristics.l,Howeverf regardless of 'thev mechanism of protective action or thereason therefore, it has been discovered by the present inventor thatthe compounds of the several categories of Table A, herein, in which thehydrocarbon substituents contain not less than 7 or more than 26 carbonatoms, and at least one of which substituents is an alkyl group on oneof the nitrogens, represents the class of compounds which are effectiveas antiozonants.

To illustrate the observed critical nature of the number of carbon atomsin the alkyl substituents, and to show how such observed data tits theabove hypothesis, there is presented herewith a diagram (FIGURE l)showing the virtual immunity (measured by the A value procedure hereinexplained) of GR-S 1500 type synthetic rubber protected from ozonecracking by parts of antiozonants or" categories II, III and V of TableA, represented by RANR'NBR" when the number of `carbon atoms in R-i-R'mof the formula (in which R and R are hydrocarbon radicals and at leastone of them is a cycloalkyl or alkyl radical and R is an arylenenucleus) is at least 7 and not more than 26, i.e., total carbon perTable A limitation 13-32 when R' is phenylene. When A and/ or B arehydrocarbon constituents the above limitations on R-i-Rm are applicableto the total hydrocarbon substituents, i.e., R-i-R|A and/ or B. In thisdiagram and A Value or 50 or less represents virtual immunity from ozoneattack; while at an A value above 500, the samples are not considered animprovement over the usual Santoex AW antioxidant control compoundsimultaneously exposed to ozone during the period of dynamic testing.When A values are obtained that lie from about 50 to about 500 the.specimens show an improvement in relation to the data on crack depthfor the control compound, i.e., the antiozonants show relative eective-Vness for ozone protection in the range above virtual immunity but stillbetter than the control. The line X represents the loss of immunity toozone attack after aging when the antiozonant is lost by migration tothe elastomer surface and volatilization; the line Y represents the lossof immunity to ozone attack when the ability of the antiozonant tomigrate to the surface is inadequate.

Diagrams similar to FIGURE l may be drawn for the antiozonants ofcategories I and iV of Table A in which A and/or B is other thanhydrogen. Since FG- URE l is typical and illustrative of the nature ofsuch diagrams, and of the carbon limits set forth in Table A forprotection of dynamic goods thereby, such further diagrams are omittedherein in the interest of brevity.

FURTHER GENERAL DESCRTPTON in the iirst part of the invention of theaforesaid joint application it is shown that anN-aryl-N'-cycloalkylpphenylenediamine (with or without hydrocarbonsubstituents on its ring structures), when incorporated into elastomercompounds in amounts exceeding 3 parte per hundred of elastomer, eiiectsprotection against ozone cracking.N-phenyl-N-l-methylcyclohexyl-p-phenylenediamine is an example of such aparent substituted diamine antiozonant, derivatives of which asindicated in Table A, have now been discovered to be antiozonants. Asshown in FiGURES 2 and 2A of said joint application, 3 parts of suchparent antiozonant per 100 ot elastomer show fair protection againstozone while virtual immunity is obtained with about 3.5 parts/ 100 ofelastomer and 0.5 part wax, when no Iantioxidants are present. With 1.5parts wax, 3.0 parts said antiozonant gives virtual immunity to ozoneattack.

it has been found that the substituted antiozonants of Table A herein,behave in a manner similar to parent antiozonants when used incombination with antioxidants and/ or waxes. This is unexpected andunpredictable in view of the diluent eiiect of substituent groups on theparent diamine. FGURE 2 is a chart drawn for one or the new antiozonantsof Table A; demonstrating synergism with antioxidants. Since FIGURE 2 isrepresentative,

further charts are unnecessary to an understanding of this part of thepresent invention, and hence have been omitted for brevity.

With the small amount of antioxidant (such as 1.25 partsphenyl-beta-naphthylamine) that is ordinarily incorporated at the rubbermanufacturing plants, substantially the same quantities of theantiozonant are required to obtain virtual immunity from ozone attack.However, the present research has shown that with larger quantities ofantioxidants present, or with certain quantities of waxes that per sehave no appreciable antiozonant effect, a synergism is developed andlesser quantities of the antiozonantswill then give virtual immunity toozone attack. The synergism of `metal salts in combination with theantiozonants of the first part of this invention is disclosed in thethird part of said copending joint application which shows thatprotection against ozone attack may be obtained with as little as 0.5part of the antiozonant material, so used.

- The amounts of synergistic rubber antioxidants and/ or waxes used inthese synergistic combinations of Part II of this invention may Varywith the specific antioxidant and/ or wax, but in general are in therange of 0.5 to 5.0 parts/ parts of elastomer. `(See FTGURE 3demonstrating synergism with two antiozonants of Table A herein.)Expressed in terms of the proportions of the synergistic composition,such composition thus may comprise from l to 9 parts of antiozonant forrubber according to Table A, from 0 to 9 parts of antioxidant forrubber, and from 0 to 9 parts wax, per l0 parts of the synergisticcomposition. (See FTGURE. 4 demonstrating the effect of increasingamounts of representative antiozonants of Table A herein.)

The amine type antioxidants which, in combination with the abovesubstituted phenylenediamines, produce good antiozonant compositions forelastomers and elastomer combinations, as above noted, includeconventionally used amine antioxidants, amine-carbonyl-condensationproducts, tetrahydroquinoline derivatives and the like. Morespecifically the antioxidants tested for forming synergistic antiozonantcombinations with the appropriately substitued phenylenediamines are setforth in Table C below; the synergistic waxes include paratlin andmicrocrystalline waxes and blends thereof.

The new antiozonants and/or the synergistic antioxidants and/or waxescan be appropriately incorporated into the elastomer'. For example theymay be added to the elastomer latex so that the final coagulatedelastomer composition contains the desired antiozonant or components ofthe synergistic antiozonant compositions of this invention, whichever isdesired. The elastomer latex may then be coagulated either in theconventional procedures, such as with sait-acid, glue, alum, etc., orwith tin and/ or iron group salts as described in Part HI of mycopending application, when the advantages thereof are desired.

Table C ANTIOXIDANTS SHOWING SYNERGISM WTH ANTIOZONANTS 1See CompoundingIngredients for Rubber, 2nd Ed., India Rubber World, 1947.

Thioamides:

Thioacetanilide 'l'hiocarbanilide Thioacetamide DibenzylthioureaPhenylacetothiomorpholide PREPARATION AND TESTING PROCEDURES Theprocedure employed in compounding and testing theelastomer-aminoadditive compositions for the examples of Tables I and l'herein was as follows: as control samples cold GR-S synthetic rubber(GR-S 1500 polymerized at 41 F. or GR-S 1600 which is the sameV exceptthat parts HAF carbon black are incorporatedV Vat the polymer plant) wascompounded and vulcanized according to best known commercial practice toobtain good aging properties. Then similar compounds were prepared andvulcanized with our new antiozonants present as additives. The recipesemployed for the several elastomer compounds were as follows:

Neozone A Medium Pine T TP-90B (plasticizer) Dioctylphthalate(plasticizer) Paraflux 2016 U Neo- Nitrile Elastomer (100 pts.) preneRubber Natural Butyl GR-S Type Hycar Rubber GR-I-l? (Cold) WHV 1014Ingredients:

Philblack O (carbon black). 50 Therrnax (carbon black) 150 Statex 125(carbon black) 40 Micronex W- (carbon black) 50 65 Zinc oxide Y 5.0 3.03.0 5 0 3.0 Steario acid 0.5 1.0 2. 5 3 0 1. 5 PBNA- 1. 0 BLE-25 1. 5

Circo Light Oil (Sull Oil C0.)

Atlantic 1115 wax Light Calcined MgO Altax d Monex e Methyl Tuads f.Santocure Sulfur Antiozonant and other additive as shown A Curingingredients are described in Compounding Ingredients for Rubber, 2nd

admon, published by India Rubber World, 1947. p

b High molecular Weight polyether sold by Thiokol Corp.

v Saturated polymerized hydrocarbon sold by C. P. Hall C0.

d Benzothiazyl disulfide.

e Tetramethyl thiuram monosulfde.

i Tetrarnethyl thiuram disulfide.

8 N-cyclohexyl-Z-benzothiazole sulfenamde.

Polycyanohydrocarbonpolyamines of Ser. No. 566,-

423, led December 30, 19552 Phenolic: Parazone (p-phenyl phenol)Santovar 0 (2,5-di-tert-butyl hydroquinone) Hydroquinone Antioxidant2246 (a p,pbisphenol) Santowhite Flakes (a dibutyl-phenyl sulfide)Santovar A (2,5-di-tert-amylhydroquinone) Phosphites:

Triphenyl phosphite v Tri(nony1phenyl) phosphite (Polygard) Aromaticesters:

Glycerol monosalicylate ester Dipropylene glycol monosalicylate ester2Corresponding Belgian Patent No. 553,700 and corresponding FrenchPatent No. 1,170,742; these cyano-alkyl amines are those containing atleast one cyano-group and at least one amino group and having a totalcarbon count per molecule of from 2 to 30 carbon atoms, which includethe alphaand beta-cyanoalkylamines, polycyanoalkylamines,

cyanoalkyl-polyamines and polycyanoalkyl polyamines falling within saidcarbon count range` proof, Heliozone and Witco 127 were found to beeiectiveV but not entirely equivalent in synergistic activity incornbination with the antiozonants of the present invention.

Forneoprene and butyl rubber the plasticization required for lowtemperature performance results in nullifying a major portion of theinherent ozone resistance of the polymer itself, and accordingly theantiozonants of the present invention are useful in suchV neoprene andbutyl stocks.

These various elastomer samples were cured at about 1000 p.s.i. in asteam heated press at 285 F. With curing times adjusted in the rangefrom 30 to 120 minutes, as required to obtain optimum tensile propertiesfor each specific compound. Samples of each of the cured stocks wereheat-aged for 24 to 48 hours at 100 C. and were then subjected to ozoneexposures in both dynamic and static tests. y

The examples in lthe tables herein are limited to sulfurcuredvulcanizates, however, sulfurless curing systems for example withtetramethylthiuramidisuliide, peroxide curing systems such as withdicumyl peroxide, benzoquinone dioxime, radiation curing systems using aradiation source such as cobalt 60, metal oxide curing of acidelastomers as for example zinc oxide and butadiene-acrylic acidcopolymers and similar curing systems can be used effectively withelastomers containing the antiozonants and synergistic antiozonantcompositions.

The dynamic ozone test was conducted on 1/2 inch dumbbell specimens ofthe vulcanizates. The exposure to ozone was carried out in analuminum-lined ozone cabinet where the concentration of ozone wasusually held at 50i5 p.p.h.m. of air. This high ozone concentration isused (25i5 p.p.h.m. is specified by ASTM test D-l 149- SlT) todemonstrate the protective eect of the antiozonants in a reasonablyshort time of evaluation and to approximate the atmospheric ozoneconcentrations reported at high altitudes attained by aircraft, and atground level in the Los Angeles areas and parts of New Mexico and Alaskaunder certain climatic conditions. Occasionally more highly acceleratedozone exposure tests were conducted by employing ozone concentrations ashigh as l5() p.p.h.m. With such high ozone concentrations much shortertimes are required to obtain valid comparisons of the protective actionof the additives under test (e.g., about 8 hours). Each sample wasstretched and relaxed continuously at a rate of 30 times per minute,between 0 and elongation on the total sample (O to 28% on the narrowportion suiering the elongation) to simulate conditions of dynamic useof the rubber. After each test, usually of 40 to 70 hours duration, aspecimen taken from the center part of the narrow part of the dumbbellwas placed under the microscope and the depth of the observed cracks wasmeasured. The depths ot the deeper 50% ot the observed cracks wereaveraged, and this average 'was designated the A value and was taken asthe index of ozone attack. With each group of 5 to l2 experimentalsamples control samples containing Santolex AW were simultaneouslysubjected to the same dynamic ozone test, and the average crack depth Avalue was compared with the A value for the crack depths ot the controlsamples as a basis of evaluation.

In the work on which this application and said copending application hasbeen based, it has been demonstrated that where antiozone protection isobtained in the dynamic tests, protection is also aorded in static use.The static tests run on both heat-aged and unaged samples showed this tobe true Without exception. (The converse is not always true, eg., somestatic protection is afforded by paraiin and microcrystalline waxes,which are valueless for protection of rubber articles subjected todynamic usages.) Specimens for static testing were mounted in accordancewith ASTM procedure DMS-44, Method B. The mounted samples were placed inthe ozone exposure cabinet wherein the ozone concentration was held at aconcentration of i5 p.p.h.m. or 50i-5 p.p.h.rn. atV a temperature of 40C. In this static test the samples were observed periodically and thetime was measured to the appearance of the first crack. Since suchstatic test data are merely conrmative of data obtained dynamically,static ozone exposure tests for the antiozonants of the presentapplication are omitted herefrom for the sake of brevity. It suffices tostate that'long continued tests show that where virtual immunity againstozone was obtained with an antiozonant or a synergistic antiozonantcomposition in a 70 hour test at 2515 p.p.h.m. of ozone or a 40 hourtest at 50i5 p.p.h.m. of ozone, static protection up to one year wasobtained at the same ozone concentration (i.e., 25 p.p.h.m.) withoutappearance of ozone cracks. The Santotlex AW controls showed severecracking in the 70 hour test and failed in about lOO hours or less underthe same static test conditions.

Similarly mountedpanels of Vspecimens (ASTM procedure D5lS-44) were alsostatically tested in outdoor weather experiments in Florida (Miami),California (Los Angeles), and Michigan (Detroit). In California, where 5highest concentrations of ozone occurred over the time of the test(varied from 5 to 6G p.p.h.m. dependent on weather variations) up to sixmonths outdoor exposure were required to develop cracks (ASTM rating 4)in the samples containing antiozonants or synergistic antiozonant TheSantotiex AW controls not only cracked but failed in a month undersimultaneous expoln the Florida and Michigan tests the protected samplesdid not crack in a one-year test whereas the control samples not onlycracked but failed in the same test. The rating method for the staticexposure tests is lo compositions.

SufC.

shown by the following tabulation:

Rating Development in Static Tests SYNERGISM In more detail, the secondpart or" the present invention comprises the discoveries ot antiozonantcompositions which rely on the action of synergistic antioxidants,parafiin and/or microcrystalline waxes in combination with specicderivativesiof dihydrocar'bon substituted p-phenyl- When used in morethan 3 parts per` 1GO parts of elastomer the said derivatives ofp-phenylenediamine Ygive virtual immunity to ozone attack per se.However, in combinations with certain antioxidants it has been foundthat reduced amounts (c g., 0.5to 3.0 pts.) of the said speciticp-phenylenediarnine derivatives in combinations with 1.5 to 6 pts. totalof specic antioxidants serve to protect elastomers against ozonedeterioration, although the antioxidants by themselves do not impartozone resistance to the elastomer compounds, nor do the reduced amountsof said specific diamino derivatives alone (i.e., in the absence of thespeciic antioxidants) show adequate protection of the elastomercompounds. Such admixed and/ or interacted components which developantiozonant activity in protection of elastomers and plastomers areenediamines.

termed herein synergistic compositions.

to herein as synergists Still another alternative interpretation of myinvention is that a small amount of a diamino derivative, which `itselfcan impart ozone resistance to elastomer and plastorner compositionsincorporating said derivative incertain minimum amounts can developozone resistance in antitoxidants when admixed therewith in less thansuch minimum amounts.

The mechanism of the action of such antioxidants in synergisticantiozonant composition is not entirely understood. One possibleexplanation is that the diamine antiozonants themselves may enter tosome extent into the complex vulcanization reactions in the curing ofthe elastomer compositions, and that the synergistic antioxidant altersthe degree to which the diamino antiozonant so enters the vulcanizationreaction. However, the exact mechanism is immaterial to the practice ofthe invention which the subsequently discussed data serve to exemplify.

It` isV also apparent Vthat the wax component is an important componentof some of the synergistic compositions. Thus Virtual immunity resultedwith 3.0 parts of the dicyanoethyl derivative ofN,N'-di-2-octyl-p-phenylenediamine antiozonant, 2.25 parts PBNA and 3parts wax (FIGURE 3); whereas with the same amounts ofthe antiozonantand PBNA but with 1.0 or 2.() parts wax virtual immunity was notattained. Similar synergistic effect of wax with other antiozonants ofthe present invention are apparent from FIGURE 3; further figures anddata, while similar have been omitted for the sake of brevity.

I have found that while paraiiin and microcrystalline kwax andcombinations thereof per se give some protection to static samples ofvulcanized elastomers no protection is afforded vulcanized elastomers indynamic usage. My findings confirm lohn O. Cole. In G. S. Whitbystreatise entitled Synthetic Rubber, published in 1954 by John Wiley &Sons, Inc., New York City, on page 541 Mr. Cole states, It'should bepointed out that, under dynamic flexing, wax offers no protection toeither GR-S or natural rubber (from the deterioration by ozone).

n In contrast to this fact I have shown that waxes when used with theantiozonants of this invention act synergistically, that is, theyenhance the protection value of the antiozonants.

YOBSERVED REsULTs Table I shows data for `antiozonants of the severalcategories of Table A incorporated in GR-S 1500 samples subjected toKthe dynamic'ozone exposure test. Table II contains examples ofantiozonants of the same categories of this invention in otherelastomers subjected to simil-ar dynamic ozone tests. 'Because ofthenecesysity of havingsep-arate controls for each group of sainplestested, samples containing Santoex AW were Itested with each group ofsamples containing other 4amino compounds to monitorV the procedure andto give assurance that the several results were valid -for evaluatingthe relative effectiveness of the several amino compounds v:forprotection of GR-S against ozone attack;

VOrthoand meta-diamino aromatic compounds are relatively inactive asantiozonantsV as disclosed in said Yelastomers because of their strongIaccelerating faction Von the vulcanization of elastomers resulting inscorchy stocks, c g., primary amino compounds such as benzidine and4-aminodiphenylamine. j

The ozone cracking in the case of the controls was Agreatly, in excessof theV 50 microns A value which represents virtual immunity to ozoneattack, while the elastomers compounded with the new antiozonants ofTable A are better than the controls and generally ap- Y are alkylgroups containing 6 to 11 carbons.

in which A is p,pbiphenylene, niethylenediphenylene, orp,p'iminodiphenylene and one or both of R and R Derivatives of theseparent antiozonants wherein the hydrogens of the just mentionedantiozonants are substituted as shown in the categories of Table A, areherewith d-is` close-d to be antiozonants for protection of variouselastomers.

Data for specimens-prepared from hot GR-S (GR-S Y 1002) were verysimilar to those for cold GR-S set forth in Table I and have therefrombeen omitted for the sake of brevity.

Likewise parent kdi-'sec-.an-"rines, which form new derivatives activeyas antiozonants and shown in Table A, are disclosed in copendinglapplications by the present inventor, such parent diamine's beingN-cyclo-hydrocarbon-Nalkylp-phenylenediarnines In similar compounds .theantiozonants of the present invention shown in the iivc categories ofTable A protect elastomers of various types against ozone.

Similarly, data for protected and unprotected polybutadiene, Phiflpreneand BS/S/AA (butadiene/styrene/ acrylic :acid terpolymer), butyl rubber,neoprene, Hycar and natural rubber further demonstrate .the extremeeffectiveness of the new antiozonants, the last four of which areexempliiicd in Table Il.

It has been demonstrated that the addition of from V1 to 5 parts of thenew antiozonants or" .this invention, Table A, increases the timepreceding appearance of the first ozone cracks inV static samples asVmuch as 1000- fold over the time of appearance of first crack insynthetic rubber articles which 'have been prepared according to thebest manner available prior to the discovery of the new antiozonants setforthV herein `as well as in the copending joint application. Data forthe dynamic test of typical antiozonants of Table A `are exemplified inFIG. 4 for the range up to 5 pts. antiozonants.

FIGURE 3 exempli-iies wax synergisrn with the new antiozonants inGli-S1500, and FIGURE 2 sho v vs synergism obtained with otherantioxidants in GR-S 1500 in combination with antiozonants of thisinvention. While data of the same type shown in FIGURES 2 and 4 havebeen obtained for antiozonants of lall categories of Table A in varioussynthetic elastomers, similar curves although not identical are omittedherein for the sake of brevity since they are merely confirmatory of thedisclosures of FIGURES 2 to 4.

A series of elastomer compounds was prepared which conclusivelyestablishes that the synergistic action with theY antiozonants of PBNA(phenyl-beta-naphthylarnine) and BLE (acetone-dipheny-larninecondensation product) in the small quantities commonly introduced at theGR-S rubber plants is relatively insignificant, and that the data basedonV compositions including commercial GR-S Vafford a valid basis forevaluation of the antiozonants per se, as well as in synergisticcombinations with other more active synergistic antioxidants and/orwit-h significant quantities of PBNA `and/or BLE.

In FIGURE 1 dynamic ozone exposure data are shown delineating thelimitations on the carbon count of the hydrocarbon substituents R-i-R"plus A and/or B, of the antiozonants of categories H, lll and V whereinA and/or B are other than nitroso or acyl groups and when R isphenylene. Such curves are the bases for the limitations shown in ltheseveral categories of Table rubber and accordingly was not incorporatedlinto the A. The interpretation of FiG. l has been considered controlcompounds. more fully hereinbefore. Finally the data for elastomercompounds show among ln comparative studies limitations on carbon countother things, (1) how the minimum of the antiozone were established for(l) specific new compositions of eective .range of carbon atoms in lthehydrocarbon submatter of categories I and IV, Table A, discovered bystituent groups is adected when at least one substituent the applicantto be effective antiozonants, and for (2) contains an aryl or cycloalkylgroup, (2) the synergistic N-nitrosoand N-acyl derivatives of categoriesI to V eiect of antioxidants, and (3) the effectiveness of theseinclusive of the invention of Table A herein, as well as diamineantiozonants even when one or both nitrogens for (3) the antiozonantsor" sm'd copending joint applicaare disubstituted. tion. For the sake ofbrevity analogous curves for such Examples D-3-4 demonstrate thatcyanoethyl radicals limitations as shown in Table A are omitted`heretrom. can replace either one or both remaining hydrogens of Forexample data for antiozonants derived from ur the parentbis-sec-alkyl-p-phenylenediamine antiozonant ther substitution ofantiozonants from said copending Without detracting from the antiozonantactivity of the joint application, said antiozonants being representedby latter, the higher molecular weight notwithstanding. the formulaR-NA-R-NBR, in which R is a As mentioned under methods of test, data forstatic member of the group comprising p,pbiphenylene, p,p' ozone testsand for outdoor weathering tests coniirm the methylenediphenylene, andp,piminodiphenylene, and dynamic test results with regard to thelantiozonant corn-V (l) both of R and R" are alkyl groups or cycloalkylpositions of the present invention, but as such tests groups or in which(2) R is aryl and R" is an alkyl or are less stringent than the dynamic4test and as such data a vcycloalkyl group, and A and/or B are as shownin are only cumulative they have been omitted herefrom Table A,demonstrate that the limitations on carbon for brevity.

Tabl'e I l count of the substituted antiozonants are applicable aslisted in Table A.

it is called to attention that Santoflex AW shows n0 protective actionagainst ozone for neoprene and butyl GR-S 1500 CONTAINING ANTIOXIDANTADDED AT TEE POLYh/IEP. PLANT; WITH ANTIOZONANTS OF TABLE A EERN NEWLYDISCOVERED BY THE PRESENT INVENTOR, USED IN SYNERGISTIC COMPOSITIONSCONTAINING PARAFFIN XVAX ACCELERATED DYNAlv/IIC OZONE EXPOSURE; OZONE:!:5 P.P.H.M.; 40 C. 111S.;30 FLEXURES PER MIN.

A Value Crack Depth (microns) Example Sample No. Pts. Additives Wax Pts.

Aged 24 Unaged hrs. at

3.0 N,N'Di2octyl-p-phenylenediamine, Lot #6 1. 5 S5 140 7.5Monostearamide of N ,Ndi2octyl-p-phenylenediamine. 1.5 30 40 3.75N,N'-Di-Z-oetyl-p-phenylenediamine-l-3.5 steal-ic acid- 1. 5 30 40 3.0NNitroso-N,N#di-2cctyl-pphenylenediamine- 1. 5 85 120 5.0N,NDi2octyl-N-methyl-p-phenylenediaxnine 1.0 30 10 6.0 Monooctanoamideof N,Ndi2octy1ppheny1enediamine 1. 5 40 50 13,0 Reaction product oi 5pts. N,Ndi-2-octyl-p-phenylenediamine and 8.55 1.5 200 450 pts. steal-ioacid (mole ratio 2/1). 2.0 Santoex AW 1. 5 200 450 5.0 Reaction productof SnO (0.03 mole); peuta(cyauoethyl)-diethylenetriamne 0 40 40 .1mole); N,Ndi(l-ethyl-B-methyl-pentyl)-p-phenylenediamine (0.15 mole);and AgeRite Resin D (0.12 mole). 2 QS2 rln 1.5 30 60 3 2.0 SautOlex AWl. 5 190 310 2.0 Santoflex AW 1. 5 250 490 5.0Ig-Butyl-N1isobutyl3rnethylbutyl-p-phenylencdiamine (l) 5 6g 251g o 5 25.0 N 2-Butyl-N'-2-trdecy1-p-phenyleuediamine 0 40 140 --do 1. 5 30 1205.0 N,N'Di2-butyl-N,N-diisobutylphenylenediamine 1. 5 150 6.0 SantoflexAW 1. 5 40 130 2.0 Santotlex l\.W 1. 5 200 270 5.0N-Diethyl-l\'cyclohexy1p-pheuylenediamine 0 U 50 dn 1. 5 (l 0 5.0N-Monccyanoethyl derivative o OZO-SB* 0 30 65 do 1.5 60 2.0 SantoexAWV 1. 5 200 265 5.0 N,NDidyanoethyl derivative of OZO-SS* 0 10 Y35 5.0N,NTetraisobutyl-p-phenylenedamine 0 50 40 5.0hrT-Cyclehexyl-N'-dimcthyl-p-phenylenediamine 0 5 g 0 o 1. 1 U 0l-Dunethyl-N 2-octylpphenylenedamine 0 0 g o l. 5 0N-Phenyl-Ndimethyl-p-phenylenediamine 0 35 40 do 1. 5 65 60 .0Dicyanoethylation derivative o N,Ndi2butylpphenylenediamine 0 l5 O 5.0Monocyauoethylation derivative of N,Ndi2buty1-p-phenylenediamine 1.0 2O5.0 Monocyaueethylaticn derivative of N,Ndi2butyl-p-phenylenediamiue 2.00

plus 2.0 pts. 1nonoeymoethyltetracthylenepentamine.

OZONE RESISTANCE OF ELASTOMER COMPOUNDS (OTHER THAN GR-S 1500)CONTAINING ANTIOZONANTS F TABLE A HEREIN (NATURAL RUBBER CONTAINED 1 PT.PBNA; NEOPRENE CONTAINED 2 PTS. NEOZONE A; NITRILE RUBBER CONTAINED 1.5PTS. BLE-) DYNAMIC OZONE EXPOSURE TEST; 40 C.; 50;i:5 P.P.H.I-/I.OZONE;30 FLEXURES PER MINUTE A Value Crack Depth (microns) ExampleElastomer Sample No. Pts. Additives Pts. Wax

Aged 24 Unaged hrs. at 100 C.

Group E 1 Natural Rubber" Control 5.0 Santoex AW 0 50 20 0 2 do -94 5.0Reaction product of SnO (0.05 mole); penta(cyanoethy] 0 Y 10 115diethylenetriamine (0.1 mole); N,N'di(1ethyl3methyl-pentyl)-p-phenylenediamine (0.13 mole); and AgeRite Resin D (0.12mole).

Neoprene Control None 0 280 340 dn R-53 5.0 Monocyanoethyl derivative ofOZO88** 0 25 65 do R-54 .-do 1. 5 K 0 0 do R 5.0N-(Z-Nonadecyl)-pphenylenediamine 1. 5 50 35 Nitrile Rubber 5.0N-Butyl-N2tridecylpphenylenediamine+ 1.5 BLE- 0 V140 300 Hycar 1014. 25.

1.5 BLE-25 1. 5 700 600 5.0Monocyanoethy1-N,Ndi2octyl-p-phenylenediamine". 0 0 75 None Y 0 130 1005.0 N,NDi2octyl-N-methyl-p-phenylenediamine 0 0 0 5.0N,N-Dimethyl-N'cyclohexylp-phenylenediamne 0 0 0 5.0 N,NDimethyl-NPhcnyl-p-phenylenediamine 0 0 0 5.0 N-Monocyanoethyl-N,Ndisec-oetylpphenylenedi 0 80 amine. f

*The cyanoalkyl and aryl derivatives of the various p-phenylenediaminesof this invention are very effective antiozonants for the nitrile typelastomers.

"See Table I footnote.

FURTHER DISCUSSION OF RESULTS Part I of this invention disclosed newantiozonants which per se in rubber containing insigniiicant amounts ofantioxidants can protect elastomers against ozone cracking. Part IIdisclosed synergistic combinations of the antiozonants of Part I withantioxidants and/ or waxes.

I have found that the quantity of antioxidant required to obtain thesynergism varies with the antioxidants used. Most of the synergisticcombinations of antiozonants of Part I of this invention in combinationwith antioxidants such as those examples of Table C contained at leastone part PBNA (added at the GR-S polymerization plants) in addition tothe added antioxidants.

From the data obtained in dynamic ozone tests it ap- Y peared that 1l ofthe antioxidants of Table C used only Vin 2 pts. per 100 pts. elastomerin combinationY with less than 3 pts. antiozonants of Table A per 100pts. elastomer do not quite attain effective protection in GR-S 1500compounds, viz:

BLE-25 Antioxidant 2246 Diphenylamine Dipropylene glycol PBNAmonosalicylate ester Rosinamine D Neozone A Flectol H Parazonel-naphthylamine Polygard which are chemically identified in Table Cabove.

But it was noted from additional data that these ll less activelysynergistic antioxidants, when augmented by the 1.25 pts. of antioxidantpresent in commercial GR-S, did give effective synergistic protection ofthe elastomer with 3 pts. or less of antiozonant similar to the examplesof FIGURE 2.

` It is accordingly shown that to attain good synergistic activity withthose less activelysynergisti'c antioxidants, it is necessary to employincreased quantities thereof, or

v some other synergist therewith.

With respect to the antiozonants of this invention, the comment asregards the insignicance of less than 1.5 parts total of antioxidants(that show significant synergism when used in greater than such amount)apply. The fact that parain wax alone is a better synergist thanmicrocrystalline wax has also been demonstrated. The data obtained withantiozonants of the present invention ness of wax as a synergist isdeveloped to a major extent' at a wax content of about 1.5 pts. Wax withvarying amounts of the antiozonant and (2) the improvements in the agedsamples from the inclusion of wax with the aitiozonant generallyparallel those in the unaged samp es.

It has been further demonstrated that the beneficial eliect of wax inoutdoor static tests is obtained. Thus 1n static usages even in theabsence of synergistic anti;- oxidants, the time to first cracking ofGR-S samples containing 2.5 ptsof antiozonants of the tive categories ofTable A can be doubled by inclusion of 1.5 pts. wax.

The categories of antiozonants of the present inven ytion (Table A) arerepresented by formula whereinR is an arylene radical selected from thegroup comprising phenylene and diphenylenc radicals and hydrocarbonsubstituted phenylene and diphenylene radicals, R is a radical selectedfrom the group comprising alkyl and cycloalkyl according to thecategories I to V; either one of A or B may be hydrogen, C1-C4 alkyl,cyanoalkyl or nitroso, and A may Yalso be an acyl group; the other of AVor B may be Cz-C.,V alkyl, cyanoalkyl or mtroso according to Table A; Ris a radical selected from the group comprising (I and 1V) sec-alkyl,(II andY V) aryl and hydrocarbon substituted aryl, and (III) cycloalkyland hydrocarbon substituted cycloalkyl; and wherein the total number ofcarbon atoms in the hydrocarbon nucleus plus hydrocarbon substituentsfor the five categories are (I) 15 to 32, (II) 13 to 31, (III) 16 to 31and (IV) l2 to 32 and (V) 17 to 31.

`In the present invention a third and/or fourth substrtuent (A or B) maybe present (according to Table A) such as C1-C4, alkyl, cyanoalkyl(C1-C19), nitroso, or polycyanoalkyl-polyamino alkyl, or acyl radical(examples of Tables I and II). In thefcase where A is acyl the molecularweight of the acyl radical has not been found to be critical, and goodantiozonant activity is evi= denced for monoacyl derivatives rangingfrom C3 to C20 or higher; C8 to C18 are preferred as the carbon range ofthe acyl group of said derivative; while these derivatives have otheradvantages the antiozone activity per unit weight of such Weight of suchderivatives is lower than for the parent compound, which disadvantagedoes not apply to other derivatives herein disclosed, eg., thosecontaining cyano hydrocarbon substituents, etc. lt has further beenfound that A and B may be nitroso, alkyl (one may be (l1-C4 and theother (I2-C4), or cyanoalkyl (C1-C19), etc. Both A and B may not beacyl.

The data also demonstrate the application of the present invention toelastomers other than hot and cold GR-S. Natural rubber, poly/butadiene,butadiene-methylvinylpyridine copolymer, butadiene-styrene-nethacrylicacid copolymers and Hycar N-rubber have been successfully protectedagainst ozone by synergistic antiozonant compositions of the presentinvention.

In summarizing the parts of this invention it has been demonstratedthat: (l) antiozonants of Table A when used in from 2 to 2.5 parts in100 parts elastomer protect the elastomer compound against ozone attack;also when A or B is acyl these antiozonants are effective antiozonantsper se, when employed in larger quantity (eg, up to 7.5 parts); (2) whenthe antiozonants oi (l) are combined with appropriate quantities ofantioxidants of the several classes of antioxidants and/ or waxes,syngeristic antiozonant compositions are formed wherein reduced amountsof antiozonants will serve to protect elastomer compositions.

The appropriate incorporation of the new antiozonant compositions, i.e.,combinations of the substituted phenylenediamines with aminoantioxidants, and/ or waxes (and/ or metal salts such as certain metalfatty acid salts of said copending joint application) gives virtumimmunity against much higher than ordinary atmospheric concentrations ofozone, to elastomer compositions, even when the same have been subjectedto radical heat-aging, thus showing that these antiozonant combinationsare capable o protectiug the products for long periods of time underdynamic as well as static conditions and at elevated temperatures.

The invention has further shown that when the total carbons of thecompounds are kept within designated ranges the antiozonants are highlyeec-tive in aged stocks, it being thus shown that the ranges arecritical for the protection of products subjected to high temperaturesresulting from dynamic usage or otherwise, but may be broadened to someextent (e.g., a carbon count of say eight carbons less than theheat-aged ranges) and still be Suitable for protection of static goodsnot subject to elevated temperatures or dynamic usages.

Comparison of the results attained, mutually and with the controls,shows that various synthetic elastomers are protected against ozone byincorporation of three to live parts of the antiozonants therein; andthe same considerations show that natural rubber is similarly protected,as well as 4polyisoprenes prepared synthetically by emulsionpolymerization processes, by alkali lmetal polymerization (e.g., Coralrubber of Firestone rlire & Rubber Co), by organo-metal alkali catalysts(eg, the Allin type of catalyst) or by metal alkyl catalysts (c g.,aluminum trialkyl, lead tetraethyl and combinations of organometalliccompoundsl with metal salts).

In addition to the examples given in the 'tables copolymers of styreneand butadiene were prepared which contained small amounts ofcopolymerized carbonyl-containing monomers such as methylvinyl ketone,crotonaldehyde or methylisopropenyl ketone and compounded with theantiozonants of this invention, and the results showed that theseantiozonants are useful as additives for these carbonyl containingelastomers.

These and other elastomers may be employed as additives, eg.,plasticizers Ifor plastomer products, for which polar elastomers areusually selected. In such cases ozone deterioration of the elastomercomponent is prevented by the antiozonants of this invention.

inn,

similar protection has been obtained with plastomer compositionscontaining ela-stomers (e.g., butyl rubber, neoprene, poly/butadiene,GR-S, acrylonitrile rubbers, etc), which per se show less susceptibilityto ozone attack.

Butyl rubber is known to be less susceptible to ozone attack than areGR-S elastomers. However, ozone cracking of butyl vulcanizates is anindustrial problem for certain uses as evidenced by the study of D. C.Edwards and E. B. Storey, Transactions of the institution of the Rubberlndustry, pp. 45-69, vol. 3l, No. 2, April 1955. l have found butylrubber when plasticized with oils as commercially practiced to beconsiderably attacked by ozone and have demonstrated that theantiozonants and synergistic antiozonant compositions of the presentinvention when appropriately compounded into butyl rubber are capable ofprotecting the resultant butyl vulcanizates against ozone attack. Inlike manner plasticized neoprene compounds are protected against ozoneattack by appropriate useof antiozonants and antiozonant compositions ofthe present invention. A

As also noted above, the elastomers used in the examples of the tablesherein generally contained antioxidant material capable of 'withstandingvulcanization, usually PENA, but sometimes BLE (chemically identied inTable C above). Such antioxidant materials atord no protection againstozone attack of the principal products, nor do they eiectively enablethe other antioxidants of Table C to do so. From the observed data,however, it is shown that in combination with the new antiozonants, thePENA and other speciiic antioxidant materials have a synergistic eilectenabling smaller quantities of the antiozonants ot the present and theother specified inventions to effectively protect the products againstozone attack.

Variations in compounding o the elastomers can nullify the protectiveaction of these antiozonants. For example, high amounts of waxes,plasticizers, zinc stearate, rosin acids or stearic acid lov/er theeiectiveness of our new additives in rubbers. Caution should beexercised by the compounder to avoid excessive amounts of suchingredients particularly Where the elastomer is subjected to dynamicuse.

In general from l to 5 pts. of the new diamine antiozonant per 1GO ofrubber in the absence of added antioxidants lis adequate for practice ofthe present invention in protection of statically employed items(prepared from natural and synthetic rubbers) for practical periods or"time against deterioration due to ozone attack; 3 or more parts arepreferred for elastomer items in dynamic usages'. In synergisticcombinations, however, brom 0.5 to 3 pts. of the substitutedp-phenylenediamines, substituted benzidines, substitutedbis(aminopheny1) amines, and substituted bis(4aminophenyl)methanes ofthis invention are sufficient to provide ozone protection for theelastomer compounds for both static and dynamic usage. When either of Aor B (of R NARNBR) is acyl as much as 7.5 pts. antiozonant/ pts.elastomer are preferred for dynamic protection.

The amount of antiozonant compositions containing synergisticantioxidants and/ or waxes required to give ozone protection toclastomers varies with the type of antioxidants and metal salts (partlll of said copending joint invention) employed and depends on whetherthe antioxidants and metal salts are used in combination or singly; ingeneral for the practice of the present invention the total amount ofsynergistic additives varies from 1.25 to 6 pts. per hundred ofelastomer. The use of small amounts ci waxes in rubber compoundstogether with antioxidants ot' course is recognized in the prior art.However, the appropriate combination of waxes with the antiozonants ofthe present invention, both with asV gistic antiozonant compositions,constitutes an unforesee- 'able and a valuable advance in the protectionof elastomer and plastomer compositions against ozone cracking, in viewof the fact that waxes were heretofore considered to be harmful forozone resistance of elastomers in dynamic usage.

The antiozonants and synergistic antiozonant compositions of the presentinvention have also been found to be effective in protection againstozone cracking of plastomers which have residual unsaturation or activehydrogens such as may be present in methylene or methinyl groups. VThusresins or plastomer compositions comprising polymers and copolymers ofVinylchloride, vinylacetate, alkylacrylates, etc'., in combination withunsaturated polymer ingredients, are subject to attack by ozone, andsuch attack is avoided when the new antiozonants are present in suchcompositions.

It has further been demonstrated that the new anti- 4ozonants andsynergistic antiozonant compositions can be as the monostearamide,oleamide, or other fatty acid Y amide, as evidenced by experimentswherein fatty acidantiozonant mixtures (l mole acid/ 1 mole diamine)were compared with the mono-acid amide in GR-S compounds and equivalentozone protection was afforded in the two cases (Examples A 2 and 3,Table I). The N nitroso derivative of N,Ndi-2octyl-p-phenylenediaminealso serves equally'well as the N,Ndi2octylp phenylenediamine for ozoneprotection (Examples A l and 4). Cyanoalkyl substituents (A and/ or B)also result in eiective diamine derivative antiozonants, e.g.,N,N-disecbutyl or di-sec-octyl-p-phenylenediamine reacted with one ortwo moles ,of lactonitrile (Examples D l, 4, 12, 13, 14, G-2, 7).Examples of A and/or B as alkyl are C 6, 9, D S to 11, and G 4 to 65 Theresearch has shown that the new compounds are valuable antiozonants forplastomers and resins as well as for natural and synthetic rubbers andare particularly useful antiozonants for tires and similar natural andsynthetic products (subject to ozone attack) which attain high operatingtemperatures, such as thosev temperatures attained by heavy duty trucktires, and such temperatures may even rise to 300 F. in use.Antiozonants are herein defined as additive agents which protect thepolymerio material, e.g., natural and synthetic rubbers, againstdeterioration due to ozone attack. While serving as antiozonants the newcompositions also serve as antioxidants, i.e., the new products of thisinvention protect against deterioration of tensile properties of rubbercompounds due to attack by Voxygen and sunlight. However, theantiozonants must not be too reactive with oxygen or they can toorapidly disappear from the compounds incorporating them and ozoneprotection will thereafter be absent. Similar to the said copending soleand joint applications, the present classes of compounds represented byY are to be used for coating and hlm-forming purposes, e.g., for papercoatings, wall paints, etc. By incorporation of the new antiozonantcompositions in the latices together with the vulcanizing ingredients,the subsequently formed cured films therefrom are edectively rprotectedagainst ozone cracking.

An antiozonant composition as used herein denotes any of the amineantiozonants represented by as herein dened, as well as each and everysynergistic composition described in the preceding discussion whethercontaining one or more of each class of synergists described, i.e.,waxes, certain metal salts, and the designated classes of antioxidants.

Herein the term elastomer is employed to designate an elastic polymer ormacromolecule, whether a naturallyoccurring material or a syntheticpolymeric substance. Plastomer is defined as including both thermosetand thermoplastic high-molecular Weight resinous and plastic materials.These deiinitions follow those used by Harry L. Fischer, Industrial andEngineering Chemistry, vol. 31, p. 942 (1939).

While there have been described rherein what are at present consideredpreferred embodiments of the invention, it will be obvious to thoseskilled in the art that minor modifications and'changes may be madeWithout departing from the essence of the invention. It is therefore tobe understood that the exemplary embodiments are illustrative and notrestrictive of the invention,-the scope of which is defined in theappended claims, and all modiiications that come within the meaning andrangeY of equivalency of the claims are intended to be included therein.

I claim:

1. A sulfur vulcanizable'rubber normally subject toV crackingcontaining, in suiiicient amount to retard said cracking, a substitutedp-phenylene diamine selected from the group consisting of thetetrasubstituted p-phenylene diamines having the formulae: Q

bon atoms, and R6 is a secondary alkyl radical containing from 8 to 9carbon atoms.

2. A sulfur vulcanizable Vrubber composition according to claim 1, inwhich the substituted p-phenylene diamine has the formula 3. A sulfurvulcanizable rubber composition according to claim 1, in which thesubstituted p-phenylene diamine has the formula 4. A sulfur vulcanizablerubber composition according to claim 1, in which the substitutedp-phenylene diamine has the formula 5. A sulfur vulcanizable rubbercomposition according to claim 1, which contains, in sufficient quantityto increase the anti-cracking eectiveness of said substitutedp-phenylene diamine, material selected from the class consisting ofgroup (a) 6-ethoXy-2,2,4trimethyl1, Z-dhydroqunoline,2,2,4-trmethyl-1,Z-dihydroquinoline polymer, dphenylamine-acetonecondensation product, phenylbeta-naphthylamine,phenyl-alpha-napthylamne, aniline acetone reaction product,aniline-butyraldehyde reaction product, di-alpha-naphthylamine,dibeta-naphthylamine, phenylenediamine (ortho, meta, and para forms),p,p' diaminodiphenylmethane, p-amino-diphenylamine, 1,2-dianilino-ethane(diphenylethylenediamine), o-tolidine, N, N-diphenyl-p-phenylenediamine,naphthylenediamine, dip-methoxydiphenylamine,N,N'-di-sec-butyl-p-phenylenediamine,N,Ndbeta-naphthyl-p-phenylenediaimne, N, N dibeta-ac-tetrahydronaphthyl-p-phenylenediamine, N,N'di-alpha-naphthyl-p-phenylenediamine,tetraethylenepentaminopropionitrile, mixture of isopropoxydiphenylamne,diphenylphenylenediamine and phenyl-betanaphthylamine,dehydroabietylamine (Rosinamine D), dodecylamine-l,N,Ntetramethylp,p'di(aminophenyl) methane,N-dimethyl-p-phenylenediamine, the cyanoalkylamues which contain atleast one cyano group and at least one amino group and have a totalcarbon count per molecule of from 2 to 30 carbon atoms, p-phenyl-References Cited by the Examiner UNITED STATES PATENTS 2,883,362 4/59Rosenwald et al. 260--45.9

FOREIGN PATENTS 3/55 Australia. 6/39 Great Britain. 4/55 Great Britain.

OTHER REFERENCES Shaw et al.: Antioxidants for GR-S Rubber, RubberWorld, August 1954, pp. 636-642.

MORRIS LIEBMAN, Primary Examiner.

PHILIP E. MANGAN, MILTON STERMAN, ALLAN M. BOETTCHER, ALPHONSO D.SULLIVAN,

Examiners.

7/57 Hand et a1. 26o-45.9 XR

1. A SULFUR VULCANIZABLE RUBBER NORMALLY SUBJECT TO CRACKING CONTAININGIN SUFFICIENT AMOUNT TO RETARD SAID CRACKING, A SUBSTITUTED P-PHENYLENEDIAMINE SELECTED FROM THE GROUP CONSISTING OF THE TETRA-SUBSTITUTEDP-PHENYLENE DIAMINES HAVING THE FORMULAE: